is_valid_date function format and validation

Hi

I am using BODS 14.1.1.210.

I am trying to validate the datetime column using the date validation function but apparently all my records fail though they are in the correct datetime format.

I was trying

is_valid_date(field, 'mm/dd/yyyy') != 0 and also tried

is_valid_datetime(field, 'mm/dd/yyyy hh:mm:ss') != 0

How can I get this function to work correctly?

Cheers!